In recent years, LEDs have begun to be used as light sources in lighting applications. As disposition of numerous LEDs and inputs of large amounts of electric power are necessary for use in lighting applications, high-thermal-radiation LED-mounting boards are required.
Conventional LED modules for mounting LEDs on LED-mounting boards adopt a configuration which conducts pattern formation of electrodes on an insulated circuit board composed of glass epoxy resin or the like, which has a reflective part designed for efficient forward reflection of light emitted from the LEDs, which includes the LEDs mounted on the bottom face of the reflective part, and which conducts resin sealing of the LEDs by means of a transparent resin with a high refractive index.
Incidentally, when light is emitted from an LED, there is the problem that the power which does not contribute to light emission is converted to heat, the temperature of the LED rises due to the emitted heat, and the light-emitting efficiency of the LED is reduced. In the case where a circuit board composed of commonly used glass epoxy resin or the like is employed as an LED mounting board for lighting, heat radiation properties are poor, and countermeasures to heat are insufficient.
As a circuit board structure with satisfactory heat radiation properties, for example, the one disclosed in Patent Document 1 has previously been provided. In this Patent Document 1, a structure is adopted where a metal plate for heat radiation is connected to the exposed face of a board interlining in order to enhance the heat radiation properties of the board.
Incidentally, the LED module 150 shown, for example, in FIGS. 9A and 9B, includes a lot of LEDs 152 which are arranged on top of a flat board 151. Through-holes 153 for fastening are formed at the four corners of this board 151.
The LED module 160 shown in FIGS. 10A, 10B and 10C forms a lot of cup structures 162 on the surface of a board 161 in order to enhance the extraction efficiency of the light emitted from the LEDs, and includes LEDs 163 mounted on the bottom of the cup structures 162. Through-holes 164 for fastening are formed at the four corners of this board 161. As an LED module of this type, for example, Patent Document 2 and 3 disclose a lighting device wherein two metal boards are combined, cup-shaped portions are formed at predetermined positions on one of the metal boards, and light-emitting elements are mounted on the bottom of their respective cup-shaped portions.
Illustration of electrodes and the like provided on the board is omitted in FIGS. 9A, 9B, and FIGS. 10A, 10B and 10C.                Patent Document 1: Japanese Unexamined Patent Application, First Publication No. S64-28886        Patent Document 2: Japanese Unexamined Patent Application, First Publication No. 2001-332768        Patent Document 3: Japanese Unexamined Patent Application, First Publication No. 2001-332769        